Abstract:

The purpose of this thesis is to explore the interconnections between evolution and structure. We explore three aspects of this question. (1) We ask how population structure influences the course of an evolutionary process. We introduce evolutionary graph theory, a theoretical approach capable of incorporating complex structures into evolutionary processes. We show that there exist structures, such as 'Super-Stars' that enormously amplify the effects of natural selection; and others, such as stem-cell architectures, that attenuate these effects. (2) We ask whether natural selection can serve as a catalyst for the emergence of structure in language and culture. We demonstrate that the English -ed rule for forming the past tense (jump/jumped) emerged as a result of the death of a large number of exceptions over a millenium. We show that the half-life of these exceptions - called irregular verbs - is proportional to the square root of their frequency, indicating that fitness plays a role in this process. Next, we explore trends in language and culture using a corpus built in collaboration with Google and comprising millions of books. We show that this approach is an extraordinarily powerful method of probing such fields as history, the humanities, and the social sciences. (3) We explore the three dimensional architecture of the genome, which compacts the genetic material - two meters in length - into a 6 micron wide nucleus. We develop Hi-C, a technology that can generate three-dimensional maps of the human genome. We use these maps to make two novel observations: first, that the genome folds up into two compartments, corresponding to active and inactive regions; second, that our data on the megabase scale is consistent with a fractal globule, a dense, organized, and totally unknotted polymer conformation which was first proposed in 1988, but that has never been observed before.